Some aspects are discussed concerning the uncertainty causes in risk assessment techniques of industrial interest. Particular attention has been paid to the evaluation of the effect of uncertainty of reliability data of devices and instruments to be used in process plants on the evaluation of the occurrence frequency of the top event. The influence of measuring equipment, whose contribution to the whole uncertainty appears in some cases very important, has been analysed with reference to both operative and environmental aspects.

DIRECTIVE 2012/18/EU of the European Parliament and of the Council of 4 July 2012 on the control of major-accident hazards involving dangerous substances, amending and subsequently repealing Council Directive 96/82/EC.